The material-removal rate (MRR) in turning is the volume of material removed per unit time, with the units of mm3/min. Referring to Figs. 21.2 and 23.3, note that, for each revolution of the workpiece,
a ring-shaped layer of material is removed which has a cross-sectional area that equals the product
of the distance the tool travels in one revolution (feed, f) and the depth of cut, d.
The volume of this ring is the product of the cross-sectional area (f)(d) and the average
circumference of the ring,